Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
2002-02-05
2003-05-27
Ngo, Hung V. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C361S816000, C361S719000
Reexamination Certificate
active
06570086
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a communication device and, more particularly, to a heat radiating structure for dissipating heat from a pyrogenic element enclosed within a housing.
BACKGROUND ART
In conventional electronic devices such as mobile communication devices, there is such a mobile communication device including a heat radiating structure for dissipating heat generated from a built-in pyrogenic element as shown in FIG.
17
.
FIG. 17
illustrates a sectioned structural diagram showing an important structure of the conventional mobile communication device disclosed in the Japanese Laid-open Patent Publication No. 11-204970. In this figure, reference numeral
1
represents a heat generating element (hereinafter referred to as a pyrogenic element), reference numeral
2
represents a printed substrate on which a communication circuitry including the pyrogenic element
1
is mounted, reference numeral
4
represents a housing for accommodating the printed substrate, and reference numeral
10
represents a heat radiating plate.
The air has a low thermal conductivity, say, 0.026 W/mK and, accordingly, where a air layer exits between the pyrogenic element
1
and the housing
4
, thermal resistance between the pyrogenic element
1
and the housing
4
is high, the temperature difference is large, and there is a problem that the pyrogenic element
1
tends to be heated to a high temperature. For this reason, a heat radiating plate
10
made of aluminum (having a thermal conductivity of 230 W/mK) or carbon (having a thermal conductivity of 500 to 800 W/mK) has one end held in tight contact with the pyrogenic element
1
, and the opposite end mounted to the inner wall of the housing
4
that is low in temperature.
With the above construction, the thermal resistance from the pyrogenic element
1
to the housing
4
is reduced and the element temperature can be lowered.
However, thermal limiting conditions of the mobile communication device include not only lowering of the element temperature, but also there is a thermal limiting condition between the element temperature and the housing temperature. By way of example, in the case of a personal computer there is no problem even if the temperature of the bottom becomes high, but the mobile telephone has to have the housing temperature limited since the instrument is often brought into contact with the user's hand and face.
With the heat radiating structure shown in
FIG. 17
, there is a problem that since the heat liberated from the pyrogenic element
1
is locally conducted to the housing
4
to which that end of the heat radiating plate
10
is mounted, a surface temperature of the housing
4
tends to become locally high.
FIG. 18
illustrates a sectioned structural diagram showing an important structure of another electronic equipment (an optical receiver) having a heat radiating function disclosed in the Japanese Laid-open Patent Publication No. 10-41678. In this figure, reference numeral
1
represents a heat generating circuit element (hereinafter referred to as a pyrogenic element) such as an amplifying circuit, a demodulating circuit or the like, reference numeral
2
represents a printed substrate on which the pyrogenic element
1
is mounted, reference numeral
3
represents a shield casing for shielding the pyrogenic element
1
, reference numeral
4
represents a housing, reference numerals
11
and
12
represent respective heat conductive sheets (having a thermal conductivity of 1 W/mK) of a silicone system or the like disposed in an air layer between the pyrogenic element
1
and the shield casing
3
and in an air layer between the shield casing
3
and the housing
4
.
Even in such construction, although as is the case with the previously described prior art, the thermal resistance between the pyrogenic element
1
and the housing
4
becomes low, the temperature difference becomes small and the element temperature can therefore be lowered, there is a problem that the surface temperature of the housing tends to be locally high since heat liberated from the element is locally conducted to an inner wall of the housing
4
to which one end of the heat conductive sheet
12
is mounted.
FIG. 19
illustrates a sectioned structural diagram showing an important structure of another electronic equipment having a heat radiating function disclosed in the Japanese Laid-open Patent Publication No. 63-124598. In this figure, reference numeral
1
represents an integrated circuit which is a heat generating circuit element (hereinafter referred to as a pyrogenic element). Reference numeral
2
represents a printed substrate on which the pyrogenic element
1
is mounted, reference numeral
3
represents a shield casing provided on an undersurface of the print substrate
2
for shielding the printed substrate
2
, and reference numeral
13
represents a thermally conductive insulating body filled between the undersurface of the printed substrate
2
and the shield casing
3
.
Although even in such construction heat liberated from the pyrogenic element
1
can be radiated, since in this prior art, the thermally conductive electrically insulating body
13
is mounted through the printed substrate, the temperature increase of an element of a thermal resistance component of the printed substrate cannot be reduced. Also, since for the thermally conductive electrically insulating body
13
, a thermally conductive material having a thermal conductivity that is relatively low as compared with that of a metallic material such as aluminum or the like ({fraction (1/100)} to {fraction (1/200)} of the thermal conductivity of aluminum) is employed, a relatively large volume of the thermally conductive material is needed to sufficiently dissipate the heat, resulting in the electronic equipment that is heavy.
FIG. 20
illustrates a sectioned structural diagram showing an important structure of another electronic equipment (a printed circuit board device) having a heat radiating function disclosed in the Japanese Laid-open Utility Model Publication No. 3-8496. In this figure, reference numeral
1
represents a semiconductor component which is a heat generating circuit element (hereinafter referred to as a pyrogenic element). Reference numeral
2
represents a printed circuit board on which the pyrogenic element
1
is mounted, and reference numeral
3
represents a shielding plate fitted to the printed circuit board
2
for electromagnetically shielding it from other printed circuit boards. Reference numeral
14
represents an L-shaped metal piece provided between the pyrogenic element
1
and the shielding plate
3
.
Although even in such construction heat liberated from the pyrogenic element
1
can be radiated through the shielding plate
3
, there is a problem in this prior art that since the metallic material is mounted in the vicinity of the semiconductor component, no electric characteristic can be warranted and the L-shaped metal piece is unable to diffuse heat sufficiently within a plane of the shielding plate
3
.
The present invention has been aimed at solving the above discussed problems and has its object to provide a communication device in which the temperature of the pyrogenic element is reduced efficiently and the surface temperature of the housing can be lowered.
DISCLOSURE OF THE INVENTION
A first communication device according to the present invention includes a communication circuit mounted on a printed substrate and having a heat generating element; a shield casing covering the communication circuit and shielding electromagnetic waves; a housing for accommodating the printed substrate having the shield casing and the communication circuit mounted thereon; a heat diffusing member mounted along an inner wall of the shield casing for diffusing heat in a planar direction; and a heat insulating layer disposed between the shield casing and an inner wall of the housing. According to this, local increase of the temperature of the housing to a high temperature can be suppressed and, also, the temp
Hasegawa Manabu
Hirao Koichi
Kobayashi Takashi
Nakao Kazushige
Ogushi Tetsurou
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Ngo Hung V.
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